Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH] x86: force inlining of test_and_set_bit and friends | Date | Sun, 7 Feb 2016 22:51:27 +0100 |
| |
Sometimes gcc mysteriously doesn't inline very small functions we expect to be inlined. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122 Arguably, gcc should do better, but gcc people aren't willing to invest time into it, asking to use __always_inline instead.
With this .config: http://busybox.net/~vda/kernel_config_OPTIMIZE_INLINING_and_Os, the following functions get deinlined many times. Examples of disassembly:
test_and_set_bit (166 copies, ~1260 calls) 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 48 0f ab 3e lock bts %rdi,(%rsi) 72 04 jb <test_and_set_bit+0xf> 31 c0 xor %eax,%eax eb 05 jmp <test_and_set_bit+0x14> b8 01 00 00 00 mov $0x1,%eax 5d pop %rbp c3 retq
test_and_clear_bit (124 copies, ~1000 calls) 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 48 0f b3 3e lock btr %rdi,(%rsi) 72 04 jb <test_and_clear_bit+0xf> 31 c0 xor %eax,%eax eb 05 jmp <test_and_clear_bit+0x14> b8 01 00 00 00 mov $0x1,%eax 5d pop %rbp c3 retq
change_bit (3 copies, 8 calls) 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 48 0f bb 3e lock btc %rdi,(%rsi) 5d pop %rbp c3 retq
clear_bit_unlock (2 copies, 11 calls) 55 push %rbp 48 89 e5 mov %rsp,%rbp f0 48 0f b3 3e lock btr %rdi,(%rsi) 5d pop %rbp c3 retq
This patch fixes this via s/inline/__always_inline/.
Code size decrease after the patch is ~13.5k:
text data bss dec hex filename 92110727 20826144 36417536 149354407 8e6f7a7 vmlinux 92097234 20826176 36417536 149340946 8e6c312 vmlinux9_bitops_after
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Graf <tgraf@suug.ch> Cc: Peter Zijlstra <peterz@infradead.org> Cc: David Rientjes <rientjes@google.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- arch/x86/include/asm/bitops.h | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/bitops.h b/arch/x86/include/asm/bitops.h index cfe3b95..7766d1c 100644 --- a/arch/x86/include/asm/bitops.h +++ b/arch/x86/include/asm/bitops.h @@ -91,7 +91,7 @@ set_bit(long nr, volatile unsigned long *addr) * If it's called on the same region of memory simultaneously, the effect * may be that only one operation succeeds. */ -static inline void __set_bit(long nr, volatile unsigned long *addr) +static __always_inline void __set_bit(long nr, volatile unsigned long *addr) { asm volatile("bts %1,%0" : ADDR : "Ir" (nr) : "memory"); } @@ -128,13 +128,13 @@ clear_bit(long nr, volatile unsigned long *addr) * clear_bit() is atomic and implies release semantics before the memory * operation. It can be used for an unlock. */ -static inline void clear_bit_unlock(long nr, volatile unsigned long *addr) +static __always_inline void clear_bit_unlock(long nr, volatile unsigned long *addr) { barrier(); clear_bit(nr, addr); } -static inline void __clear_bit(long nr, volatile unsigned long *addr) +static __always_inline void __clear_bit(long nr, volatile unsigned long *addr) { asm volatile("btr %1,%0" : ADDR : "Ir" (nr)); } @@ -151,7 +151,7 @@ static inline void __clear_bit(long nr, volatile unsigned long *addr) * No memory barrier is required here, because x86 cannot reorder stores past * older loads. Same principle as spin_unlock. */ -static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr) +static __always_inline void __clear_bit_unlock(long nr, volatile unsigned long *addr) { barrier(); __clear_bit(nr, addr); @@ -166,7 +166,7 @@ static inline void __clear_bit_unlock(long nr, volatile unsigned long *addr) * If it's called on the same region of memory simultaneously, the effect * may be that only one operation succeeds. */ -static inline void __change_bit(long nr, volatile unsigned long *addr) +static __always_inline void __change_bit(long nr, volatile unsigned long *addr) { asm volatile("btc %1,%0" : ADDR : "Ir" (nr)); } @@ -180,7 +180,7 @@ static inline void __change_bit(long nr, volatile unsigned long *addr) * Note that @nr may be almost arbitrarily large; this function is not * restricted to acting on a single-word quantity. */ -static inline void change_bit(long nr, volatile unsigned long *addr) +static __always_inline void change_bit(long nr, volatile unsigned long *addr) { if (IS_IMMEDIATE(nr)) { asm volatile(LOCK_PREFIX "xorb %1,%0" @@ -201,7 +201,7 @@ static inline void change_bit(long nr, volatile unsigned long *addr) * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ -static inline int test_and_set_bit(long nr, volatile unsigned long *addr) +static __always_inline int test_and_set_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", "c"); } @@ -228,7 +228,7 @@ test_and_set_bit_lock(long nr, volatile unsigned long *addr) * If two examples of this operation race, one can appear to succeed * but actually fail. You must protect multiple accesses with a lock. */ -static inline int __test_and_set_bit(long nr, volatile unsigned long *addr) +static __always_inline int __test_and_set_bit(long nr, volatile unsigned long *addr) { int oldbit; @@ -247,7 +247,7 @@ static inline int __test_and_set_bit(long nr, volatile unsigned long *addr) * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ -static inline int test_and_clear_bit(long nr, volatile unsigned long *addr) +static __always_inline int test_and_clear_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", "c"); } @@ -268,7 +268,7 @@ static inline int test_and_clear_bit(long nr, volatile unsigned long *addr) * accessed from a hypervisor on the same CPU if running in a VM: don't change * this without also updating arch/x86/kernel/kvm.c */ -static inline int __test_and_clear_bit(long nr, volatile unsigned long *addr) +static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long *addr) { int oldbit; @@ -280,7 +280,7 @@ static inline int __test_and_clear_bit(long nr, volatile unsigned long *addr) } /* WARNING: non atomic and it can be reordered! */ -static inline int __test_and_change_bit(long nr, volatile unsigned long *addr) +static __always_inline int __test_and_change_bit(long nr, volatile unsigned long *addr) { int oldbit; @@ -300,7 +300,7 @@ static inline int __test_and_change_bit(long nr, volatile unsigned long *addr) * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ -static inline int test_and_change_bit(long nr, volatile unsigned long *addr) +static __always_inline int test_and_change_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", "c"); } @@ -311,7 +311,7 @@ static __always_inline int constant_test_bit(long nr, const volatile unsigned lo (addr[nr >> _BITOPS_LONG_SHIFT])) != 0; } -static inline int variable_test_bit(long nr, volatile const unsigned long *addr) +static __always_inline int variable_test_bit(long nr, volatile const unsigned long *addr) { int oldbit; @@ -343,7 +343,7 @@ static int test_bit(int nr, const volatile unsigned long *addr); * * Undefined if no bit exists, so code should check against 0 first. */ -static inline unsigned long __ffs(unsigned long word) +static __always_inline unsigned long __ffs(unsigned long word) { asm("rep; bsf %1,%0" : "=r" (word) @@ -357,7 +357,7 @@ static inline unsigned long __ffs(unsigned long word) * * Undefined if no zero exists, so code should check against ~0UL first. */ -static inline unsigned long ffz(unsigned long word) +static __always_inline unsigned long ffz(unsigned long word) { asm("rep; bsf %1,%0" : "=r" (word) @@ -371,7 +371,7 @@ static inline unsigned long ffz(unsigned long word) * * Undefined if no set bit exists, so code should check against 0 first. */ -static inline unsigned long __fls(unsigned long word) +static __always_inline unsigned long __fls(unsigned long word) { asm("bsr %1,%0" : "=r" (word) @@ -393,7 +393,7 @@ static inline unsigned long __fls(unsigned long word) * set bit if value is nonzero. The first (least significant) bit * is at position 1. */ -static inline int ffs(int x) +static __always_inline int ffs(int x) { int r; @@ -434,7 +434,7 @@ static inline int ffs(int x) * set bit if value is nonzero. The last (most significant) bit is * at position 32. */ -static inline int fls(int x) +static __always_inline int fls(int x) { int r; -- 1.8.1.4
| |